Recent advances in the diagnosis, classification and molecular pathogenesis of cutaneous mesenchymal neoplasms

The diagnosis of cutaneous mesenchymal neoplasms remains challenging, due to a combination of overlapping histological features, the rarity of some diagnoses and often inadequate sampling in superficial biopsies. Here, we describe recent advances in cutaneous mesenchymal neoplasms. We discuss improvements in our understanding of the molecular pathogenesis of non-neural granular cell tumour, epithelioid fibrous histiocytoma, composite and retiform haemangioendothelioma and dermatofibrosarcoma protuberans. We also discuss recently described tumour types, including some discovered via molecular testing: EWSR1::SMAD3-rearranged fibroblastic tumour, clear cell neoplasm with MITF::CREM rearrangement and melanocytoma with CRCT1::TRIM11 rearrangement, and some discovered via traditional histopathology: superficial CD34-positive fibroblastic tumour, plexiform myofibroblastoma and clear cell neoplasm with melanocytic differentiation and ACTIN::MITF translocation.